Problem: If $a + b + c = -1$ and $x + y = 6$, what is $5x + 5y + 10b + 10a + 10c$ ?
Solution: $= 10a + 10b + 10c + 5x + 5y$ $= (10) \cdot (a + b + c) + (5) \cdot (x + y)$ $= (10) \cdot (-1) + (5) \cdot (6)$ $= -10 + 30$ $= 20$